The present invention is related to a shelf convention system comprising a shelf transport vehicle configured to transport a shelf having a plurality of shelf legs.
In recent years, there have been a growing number of, for example, warehouses or factories handling a wide variety of products, such as a mail-order warehouse or a high-mix low-volume production factory, in order to flexibly satisfy increasingly diverse consumer needs, and there has been a demand for promotion of work efficiency and automation in, for example, warehouses or factories.
There is known a technology of a shelf transport vehicle transporting a shelf storing products in order to automate those tasks. In relation to this technology, JP 2009-539727 A, JP 2014-089740 A, and JP 2002-182744 A are known.
In JP 2009-539727 A, there is a description “A system for transporting inventory items includes an inventory holder capable of storing inventory items and a mobile drive unit. The mobile drive unit is capable of moving to a first point with the inventory holder at least one of coupled to and supported by the mobile drive unit. The mobile drive unit is additionally capable of determining a location of the inventory holder and calculating a difference between the location of the inventory holder and the first point. The mobile drive unit is then capable of determining whether the difference is greater than a predetermined tolerance. In response to determining that the difference is greater than the predetermined tolerance, the mobile drive unit is also capable of moving to a second point based on the location of the inventory holder, docking with the inventory holder, and moving the mobile drive unit and the inventory holder to the first point.” (refer to Abstract).
In JP 2014-089740 A, there is a description “A plurality of pairs of shape information on a predetermined area on a preset environmental map and properties of the predetermined area on the environmental map are stored, the predetermined area stored in a storage part is compared with the environmental map, and properties corresponding to the predetermined area are read out so as to update the environmental map according to properties of a measurement place.” (refer to Abstract).
In JP 2002-182744 A, there is a description “The unmanned carrier is provided with a function which approaches the leg parts of the pallet having leg parts while lowering a load carrying platform, raises the load carrying platform and carries and transports the pallet. At the time of invasion to the pallet, an approach sensor scanning laser beams and detecting a distance and an angle detects a distance to both leg parts of the pallet, operates an inclination with respect to the center line of the pallet and a distance to the center line and guides the carrier so that the center line of the unmanned carrier is matched with the center line of the pallet. A side sensor detecting an interval to the leg parts of the pallet arranged on the side of a car body guides the carrier after approaching the pallet.” (refer to Abstract).
Further, JP 2011-150443 A is known as a technology of an unmanned rack conveyance vehicle recognizing, for example, the position of another unmanned rack conveyance vehicle. In JP 2011-150443 A, there is a description “A first robot includes: a measurement part measuring the reflection light intensity of an object; an arithmetic part analyzing a measurement result obtained by the measurement part; and a drive part moving the first robot. A second robot includes a plurality of markers each having a retroreflection property. The arithmetic part of the first robot calculates positions of the plurality of markers of the second robot based on a measurement result of the measurement part, recognizes a position and an attitude of the second robot based on a result of the calculation, and calculates a parameter for moving the first robot based on a result of the recognition of the position and the attitude of the second robot. The drive part of the first robot moves the first robot based on the parameter.” (refer to Abstract).
At the time of introduction of the system including an unmanned shelf transport vehicle, shelves storing products are required to be aligned at a predetermined location. In the system of JP 2009-539727 A, the position of a shelf is required to be grasped in order for the unmanned shelf transport vehicle to transport the shelf. However, shelves before being aligned are arranged dispersedly, and workers are required to align those shelves by themselves because the unmanned shelf transport vehicle cannot grasp the positions.
Meanwhile, the unmanned shelf transport vehicle has a function of recognizing its own position, and moves along a path set by an unmanned shelf transport vehicle management apparatus for managing the unmanned shelf transport vehicle based on its own recognized position. In JP 2009-539727 A, the unmanned shelf transport vehicle reads a marker on the floor to recognize its own position, and in JP 2014-089740 A, the unmanned shelf transport vehicle compares an environmental map with a measurement result of a distance sensor to recognize its own position. However, with any of those methods, the unmanned shelf transport vehicle may fail to recognize and track its own position. For example, with the method of JP 2009-539727 A, when the unmanned shelf transport vehicle has moved out of the path due to, for example, slip of a tire, the unmanned shelf transport vehicle cannot read the marker and fails to track its own position. Further, with the method of JP 2014-089740 A, when the unmanned shelf transport vehicle is surrounded by other unmanned shelf transport vehicles, the measurement result of the distance sensor is not matched with the environmental map, and the unmanned shelf transport vehicle fails to track its own position. In this manner, when the unmanned shelf transport vehicle has failed to track its own position, the unmanned shelf transport vehicle cannot recognize its own position again unless workers return the unmanned shelf transport vehicle to a predetermined position.
Even when the absolute positions of shelves before being aligned at the time of introduction of the system cannot be grasped, the unmanned shelf transport vehicle can get under a shelf to transport the shelf by recognizing its own position and attitude relative to the shelf. Further, when the unmanned shelf transport vehicle has failed to track its own position, the unmanned shelf transport vehicle recognizes its own position and attitude relative to a shelf to get under the shelf. In this case, when the unmanned shelf transport vehicle gets under the shelf, the unmanned shelf transport vehicle can read identification information (e.g., a barcode attached to the bottom of the shelf) on the shelf. The unmanned shelf transport vehicle transmits the read identification information on the shelf to the unmanned shelf transport vehicle management apparatus, which grasps the position of the shelf, and the unmanned shelf transport vehicle management apparatus notifies the unmanned shelf transport vehicle of the position of the shelf, to thereby enable the unmanned shelf transport vehicle to recognize its own position. In this manner, it is important for the unmanned shelf transport vehicle to recognize its own position and attitude relative to the shelf.
In JP 2002-182744 A, there is disclosed an unmanned carrier configured to detect a center line of a pallet based on the measurement result of the distance sensor and get under the pallet on the detected center line. However, this disclosure is based on the assumption that there is only one pallet within the measurement range of the distance sensor, and the unmanned carrier falsely recognizes a pallet when there are a plurality of pallets within the measurement range of the distance sensor.
Further, in JP 2011-150443 A, it is assumed that an object has a continuous surface. When the unmanned shelf transport vehicle can get under a shelf, the distance sensor of the unmanned shelf transport vehicle can measure only the legs of the shelf, and thus the method disclosed in JP 2011-150443 A cannot be applied to the shelf.